JP6386462B2 - Composite structure - Google Patents

Description

The present invention relates to a composite structure applicable to joining a steel pipe and a member to be joined.
This application claims priority on September 25, 2013 based on Japanese Patent Application No. 2013-197688 for which it applied to Japan, and uses the content here.

Conventionally, in order to improve the bond strength between steel pipe piles and concrete, it is common to provide protrusions on at least one of the inner and outer peripheral surfaces of the tip of the steel pipe piles to prevent slippage between the steel pipe piles and the concrete. Known to.

In Patent Document 1 below, by providing an annular protrusion on the inner peripheral surface of the steel pipe pile along the circumferential direction of the steel pipe pile as a slip stopper between the steel pipe pile and the concrete, the integrity of the steel pipe pile and the concrete is improved. A technique for ensuring and improving the adhesion strength is disclosed.

In Patent Documents 2 and 3 below, by providing a spiral protrusion on the inner peripheral surface or outer peripheral surface of the steel pipe pile as a slip stopper between the steel pipe pile and the concrete, the integrity of the steel pipe pile and the concrete is secured. A technique for improving the adhesion strength is disclosed.

In Non-Patent Document 1 below, as a method of manufacturing a steel pipe pile in which a spiral protrusion is provided on the inner peripheral surface or the outer peripheral surface, a spiral protrusion is formed by winding a steel strip provided with the protrusion spirally. A method of manufacturing a steel pipe pile having the same is disclosed. In Non-Patent Document 1, since the bond strength between the steel pipe pile and the concrete is reduced due to the increase in the spiral protrusion direction angle, in order to ensure the predetermined bond strength between the steel pipe pile and the concrete, The spiral projection direction angle is limited to 40 ° or less.

Non-Patent Document 2 below discloses the results of an experiment conducted for investigating the adhesion strength between a steel pipe having a spiral protrusion provided on the inner peripheral surface and concrete. This experimental result shows that the necessary adhesion strength between the steel pipe and the concrete can be secured even when the spiral protrusion direction angle is 45 °.

Japanese Laid-Open Patent Publication No. 2007-51500 Japanese Unexamined Patent Publication No. 2007-32044 Japanese Unexamined Patent Publication No. 8-284159

JIS A 5525 “Steel pipe pile” “Adhesive properties of lap joints with ribbed steel pipes”, Annual Meeting of the Japan Society of Civil Engineers, Vol. 5, Vol. 50, pp. 880-881, 1995

However, in the steel pipe piles disclosed in Patent Documents 1, 2, and 3, the cross-sectional rigidity and member strength of the stiffening region (the region in contact with the concrete on the inner peripheral surface of the steel pipe pile) are the same. It is significantly different from the area that does not come into contact with concrete on the peripheral surface. In particular, the cross-sectional rigidity and member strength of the steel pipe pile are greatly reduced at the boundary between the stiffening region and the raw pipe region of the steel pipe pile.

For this reason, in the steel pipe pile disclosed in Patent Documents 1, 2, and 3, when loads such as bending force, axial force, and shearing force are applied to the steel pipe pile, the stiffening region and the raw tube region of the steel pipe pile At the boundary, stress concentration due to the above-described load may occur, and local buckling may occur in the raw tube region.

In addition, as described above, when local buckling occurs in the raw pipe region of the steel pipe pile, the support of the building structure or the like may be insufficient at the joint between the upper column of the building structure and the steel pipe pile. There is sex.

One method for preventing local buckling in the raw pipe region of such steel pipe piles is to increase the plate thickness of the steel pipe piles. However, if the method of increasing the thickness of the steel pipe pile is adopted, the weight of the steel pipe pile increases and the material cost increases, so this method is not rational. Further, as another method for preventing local buckling in the raw pipe region of the steel pipe pile, it may be possible to install a stiffener or other stiffener in the raw pipe region, but this increases the labor of processing.

The present invention has been made in view of the above circumstances, and without increasing the plate thickness of the steel pipe, and without using a stiffener or other stiffener, the stiffening region and the raw tube region of the steel pipe An object of the present invention is to provide a composite structure capable of improving local buckling resistance at the boundary.

The present invention employs the following means in order to solve the above problems and achieve the object.
(1) The composite structure according to an aspect of the present invention includes a steel pipe; a member to be joined whose one end is inserted into the steel pipe; and an inner peripheral surface of the steel pipe and the one end of the member to be joined. Filled concrete; and The steel pipe has a protrusion that protrudes inward in the radial direction of the steel pipe from the inner peripheral surface of the steel pipe and extends spirally along the pipe axis direction of the steel pipe. When the region in contact with the concrete on the inner peripheral surface of the steel pipe is defined as a stiffening region and the region not in contact with the concrete on the inner peripheral surface of the steel pipe is defined as a raw tube region, the protrusion is It extends in the spiral shape along the tube axis direction so as to straddle the boundary between the stiffening region and the raw tube region. The extension length of the projection in the pipe axis direction in the raw pipe region is equal to or greater than the local buckling half wavelength of the steel pipe. When the projection is viewed from the inside in the radial direction of the steel pipe, an angle between the circumferential direction of the steel pipe and the projection is 30 ° or more and less than 90 °. When the local buckling half wavelength of the steel pipe is defined as λ (mm), the outer diameter of the steel pipe is defined as D (mm), and the plate thickness of the steel pipe is defined as t (mm), the local buckling half wavelength λ is It is represented by the following formula (1), and the ratio D / t between the outer diameter D and the plate thickness t of the steel pipe is 50 or more and 100 or less.

( 2 ) In the composite structure according to (1) above, when the steel pipe is viewed in a cross section parallel to the tube axis direction, the convex cross section of the protrusion has the local buckling half-wavelength along the tube axis direction. They may be arranged at intervals of λ or less.

According to the composite structure described in (1) above, at the boundary between the stiffening region and the raw tube region of the steel pipe, the difference in cross-sectional rigidity and member strength between the stiffening region and the raw tube region of the steel pipe is reduced. It is possible to gradually reduce the cross-sectional rigidity and member strength of the steel pipe from the rigid region to the raw tube region, thereby preventing a rapid decrease in the cross-sectional rigidity and member strength of the steel pipe.

According to the composite structure described in the above (1), it is possible to prevent a sudden decrease in the cross-sectional rigidity and the member strength of the steel pipe at the boundary between the stiffening region and the raw pipe region of the steel pipe, and thereby the bending force, the axial force, the shearing force. Occurrence of stress concentration on the steel pipe due to a load such as force can be avoided, and local buckling in the raw pipe region can be prevented.

According to the composite structure described in the above (1), since the local buckling resistance of the steel pipe can be improved at the boundary between the stiffening region and the raw pipe region of the steel pipe, the joint location between the steel pipe and the member to be joined It is possible to provide sufficient support for building structures and the like.

According to the composite structure described in ( 1 ) above, the thin portion of the steel pipe where no protrusion is present is not continuous in the pipe circumferential direction cross section. As a result, since local buckling resistance of the steel pipe can be improved, it is possible to prevent the occurrence of local buckling in the raw pipe region.

In addition, according to the composite structure described in ( 1 ) above, it is possible to reliably prevent the local buckling of the steel pipe such that the pipe wall is crushed like a bellows. In addition, it is possible to reliably adhere the concrete to the inner peripheral surface of the steel pipe, and to sufficiently secure the adhesion strength between the steel pipe and the concrete.

According to the composite structure described in ( 1 ) above, the protrusion provided in the stiffening region in order to improve the adhesion strength between the steel pipe and the concrete can be further extended along the pipe axis direction of the steel pipe. It becomes possible to efficiently manufacture a steel pipe with improved local buckling resistance.

In particular, conventionally, when the protrusion is provided on the steel pipe only for the purpose of ensuring the adhesion strength between the steel pipe and the concrete, the protrusion is inclined by about 10 ° to 20 ° with respect to the circumferential direction of the steel pipe. However, according to the composite structure described in ( 1 ) above, the manufacturing process of the steel pipe in which the protrusion is provided in order to secure the adhesion strength between the steel pipe and the concrete is directly utilized, and the steel pipe is 30 in the circumferential direction. It is possible to efficiently provide the protrusion with the local buckling resistance of the steel pipe improved by inclining the protrusion at an angle of more than 0 °.

According to the composite structure described in ( 2 ) above, local buckling occurs in the raw pipe region due to the load acting on the steel pipe between the protrusions adjacent to each other along the pipe axis direction of the steel pipe. It becomes possible to prevent.

It is a longitudinal section showing composition structure 1 concerning one embodiment of the present invention. It is an enlarged view of the area | region C enclosed with the dotted line in FIG. FIG. 2 is an enlarged view of a region including a boundary between a stiffening region B1 and a raw tube region B2. It is a figure which shows typically each with the case where the shear force Q is made to act on the steel pipe pile 10, and the case where the axial force N is made to act on the steel pipe pile 10. FIG. A graph in which “L / √ (D · t)” in Table 1 is set as the horizontal axis and “Q _max / Q0” in Table 1 is set as the vertical axis is shown. 3 is a graph in which the protrusion inclination angle θ in Table 2 is set as the horizontal axis, and “Q _max / Q0” in Table 2 is set as the vertical axis. The projection inclination angle θ in Table 3 is set as the horizontal axis, and “N _max / N0) in Table 3 is set as the vertical axis. The graph in which “S / √ (D · t)” in Table 4 is set as the horizontal axis and “Q _max / Q0” in Table 4 is set as the vertical axis is shown. It is a figure which shows the modification of this embodiment. It is a figure which shows the modification of this embodiment.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a longitudinal sectional view showing a composite structure 1 according to an embodiment of the present invention. As shown in FIG. 1, the composite structure 1 according to this embodiment includes a steel pipe pile 10 (steel pipe) driven into the ground, and an H-section steel 20 (member to be joined) having one end inserted into the steel pipe pile 10. The concrete 30 filled between the inner peripheral surface 11 of the steel pipe pile 10 and the one end part (part inserted in the steel pipe pile 10) of the H-section steel 20 is provided. In addition, FIG. 1 is the figure which looked at the steel pipe pile 10 in the cross section parallel to the pipe-axis direction (Y direction in FIG. 1) of the steel pipe pile 10. FIG.

  The H-section steel 20 is a pillar member of a building structure (upper structure), for example. Concrete 30 is provided between the inner peripheral surface 11 of the steel pipe pile 10 and one end of the H-shaped steel 20 in a state where one end of the H-shaped steel 20 is inserted into the steel pipe pile 10 driven into the ground as a foundation structure. By being filled, the steel pipe pile 10 and the H-section steel 20 are joined to each other. As shown in FIG. 1, a base plate 21 is preferably joined to the tip of the H-section steel 20 in order to increase the joint strength between the steel pipe pile 10 and the H-section steel 20. However, the base plate 21 is not essential.

The steel pipe pile 10 is, for example, a steel pipe having an outer diameter D of 1000 mm, a plate thickness t of 6.6 mm, and a Poisson's ratio ν of 0.28 to 0.30. The outer diameter D, the plate thickness t, and the Poisson's ratio ν of the steel pipe pile 10 are not limited to the above numerical values. However, if the plate thickness t of the steel pipe pile 10 is too large, there is a merit that the local buckling resistance of the steel pipe pile 10 is increased, but there is also a demerit that the weight and material cost of the steel pipe pile 10 are increased. Therefore, in this embodiment, the ratio D / t between the outer diameter D and the plate thickness t is set to 50 or more and 100 or less in consideration of the balance between the merit and demerit caused by the plate thickness t.
When a steel material for construction is used as the steel pipe pile 10, when the ratio D / t between the outer diameter D and the plate thickness t is less than 50, a decrease in yield strength due to local buckling occurs in the steel pipe pile 10. Therefore, it is desirable to set the lower limit value of the ratio D / t to 50. On the other hand, the upper limit value of the ratio D / t is not particularly limited, but the upper limit value of the ratio D / t of the steel pipe manufactured for civil engineering and distributed in the market is approximately 100. Also, the upper limit value of the ratio D / t of the steel pipe pile 10 is set to 100.
Such a steel pipe pile 10 protrudes from the inner peripheral surface 11 of the steel pipe pile 10 inward in the radial direction (X direction in FIG. 1) of the steel pipe pile 10 and spirals along the pipe axis direction Y of the steel pipe pile 10. It has the protrusion 12 extended in the shape.

  FIG. 2 is an enlarged view of a region C surrounded by a dotted line in FIG. As shown in FIG. 2, the length of the convex cross section of the protrusion 12 in the pipe axis direction Y of the steel pipe pile 10 is defined as the protrusion width w. Moreover, the length of the convex cross section of the protrusion 12 in the radial direction X of the steel pipe pile 10 is defined as the protrusion height h. Further, the distance between the centers of the convex cross sections of the protrusions 12 adjacent to each other along the tube axis direction Y is defined as a protrusion interval S. Furthermore, when the projection 12 is viewed from the inside in the radial direction X of the steel pipe pile 10, an angle between the circumferential direction (W direction in FIG. 2) of the steel pipe pile 10 and the projection 12 is defined as a projection inclination angle θ.

  The protrusion width w of the protrusion 12 is, for example, 10 mm. The protrusion height h of the protrusion 12 is, for example, 4 mm. However, the protrusion width w and the protrusion height h of the protrusion 12 are not limited to the above numerical values. The protrusion inclination angle θ is preferably 30 ° or more and less than 90 °. The protrusion inclination angle θ is most preferably 30 ° or more and less than 60 °. The reason why it is preferable to set the protrusion inclination angle θ in the above range will be described later. A preferable range of the protrusion interval S will be described later. In addition, in this embodiment, although the case where the processus | protrusion 12 which has a rectangular-shaped convex cross section was formed in the steel pipe pile 10, the shape of the convex cross section of the processus | protrusion 12 may be shapes other than a rectangle.

  The protrusion 12 may be provided on the inner peripheral surface 11 of the steel pipe pile 10 by rolling of a steel strip or the like, or may be provided by attaching a steel bar by welding or placing a weld bead. Moreover, the some protrusion 12 inclined in a mutually different direction with respect to the circumferential direction W of the steel pipe pile 10 may be combined by making some helical protrusions 12 cross | intersect mutually. Moreover, the spiral protrusion 12 and the protrusion 12 parallel to the circumferential direction W of the steel pipe pile 10 may be combined.

Below, as shown in FIG. 1, the area | region in which the protrusion 12 is provided in the inner peripheral surface 11 of the steel pipe pile 10 is defined as protrusion area | region A1, and the protrusion 12 is provided in the inner peripheral surface 11 of the steel pipe pile 10. A region that does not exist is defined as a flat region A2. In addition, as shown in FIG. 1, a region that contacts the concrete 30 on the inner peripheral surface 11 of the steel pipe pile 10 is defined as a stiffening region B1, and a region that does not contact the concrete 30 on the inner peripheral surface 11 of the steel pipe pile 10 is defined. This is defined as a tube region B2.

  As shown in FIG. 1, the protrusion 12 is spirally extended along the tube axis direction Y so as to straddle the boundary between the stiffening region B1 and the raw tube region B2. In other words, in the projection region A1, there is at least one boundary between the stiffening region B1 and the raw tube region B2. Although details will be described later, there may be two boundaries between the stiffening region B1 and the raw tube region B2 in the projection region A1.

  As shown in FIG. 1, the length of the protrusion 12 extending along the tube axis direction Y from the boundary between the stiffening region B1 and the raw tube region B2 toward the raw tube region B2 is defined as an extended length L. Define. In other words, the extending length L in the tube axis direction Y of the protrusion 12 in the raw tube region B2 subtracts the length in the tube axis direction Y of the stiffening region B1 from the length in the tube axis direction Y of the protrusion region A1. This is the length obtained.

FIG. 3 is an enlarged view of a region including the boundary between the stiffening region B1 and the raw tube region B2 in FIG. As shown in FIG. 3, the extending length L in the tube axis direction Y of the protrusion 12 in the raw tube region B <b> 2 is equal to or greater than the local buckling half wavelength λ of the steel pipe pile 10. Here, the local buckling half-wavelength λ of the steel pipe pile 10 is due to the fact that loads such as bending force M, axial force N, and shearing force Q act on the steel pipe pile 10, so This is the length of the buckled portion 13 generated on the tube wall of the raw tube region B2 close to the boundary with the region B2 (see FIG. 3).

As described above, when the outer diameter of the steel pipe pile 10 is defined as D (mm), the plate thickness of the steel pipe pile 10 is defined as t (mm), and the local buckling half wavelength of the steel pipe pile 10 is defined as λ (mm), The buckling half wavelength λ is expressed by the following formula (1). In addition, when the Poisson's ratio of the steel pipe pile 10 is defined as ν, the constant K in the following formula (1) is represented by the following formula (2).

Further, as shown in FIG. 3, when the steel pipe pile 10 is viewed in a cross section parallel to the pipe axis direction Y, the convex cross section of the protrusion 12 is spaced along the pipe axis direction Y at a local buckling half wavelength λ or less. It is desirable to line up. In other words, it is desirable that the protrusion interval S of the protrusions 12 is equal to or less than the local buckling half wavelength λ. That is, it is desirable that the relationship between the extended length L of the protrusions 12, the protrusion interval S, and the local buckling half-wavelength λ satisfy the following conditional expression (3).
S ≦ λ ≦ L (3)

  According to the composite structure 1 having the above-described configuration, the stiffening region B1 and the raw pipe of the steel pipe pile 10 can be used without increasing the plate thickness of the steel pipe pile 10 and without using a stiffener or other stiffener. It is possible to improve the local buckling resistance at the boundary with the region B2. That is, according to the composite structure 1 having the above-described configuration, the condition (the ratio D / outer diameter D to the thickness t) where the balance between the merit and the demerit due to the thickness t of the steel pipe pile 10 is optimal. The local buckling resistance at the boundary between the stiffening region B1 and the raw tube region B2 can be improved while satisfying the condition that t is 50 or more and 100 or less.

  Below, as shown in FIG. 4, the local buckling resistance of the steel pipe pile 10 is shown for each of the case where the shear force Q is applied to the steel pipe pile 10 and the case where the axial force N is applied to the steel pipe pile 10. The result analyzed by the finite element method (FEM) analysis using a shell element is demonstrated.

In the above FEM analysis, the outer diameter D of the steel pipe pile 10 is 1000 mm, the plate thickness t of the steel pipe pile 10 is 6.6 mm, the Poisson's ratio ν of the steel pipe pile 10 is 0.30, the protrusion height h of the protrusion 12 is 4 mm, The protrusion width w of the protrusion 12 was set to 10 mm, the protrusion inclination angle θ of the protrusion 12 was set to 30 °, and the protrusion interval S of the protrusion 12 was set to 100 mm. Under such conditions, the local buckling half wavelength λ of the steel pipe pile 10 is 199 mm.
Under the above conditions, when the extension length L of the protrusion 12 is changed in the range of 0 mm to 500 mm, the local buckling resistance against the extension length L of the protrusion 12 and the shear force Q (maximum proof stress against the shear force Q). Table 1 below shows the results of analyzing the relationship with In Table 1 below, when the extended length L of the protrusion 12 is 199 mm or more, the condition that the extended length L of the protrusion 12 is equal to or greater than the local buckling half wavelength λ of the steel pipe pile 10 is satisfied.

In Table 1, Q _max (kN) is a local increase in the steel pipe pile 10 when the steel pipe pile 10 is forcibly deformed by gradually increasing the shearing force Q acting on the upper end of the steel pipe pile 10. The shearing force Q when the buckling occurs and the maximum proof stress is reached is shown. That is, this Q _max indicates the local buckling resistance of the steel pipe pile 10 with respect to the shearing force Q (maximum proof stress with respect to the shearing force Q).
The maximum proof stress Q _max (= 794 kN) when the extended length L is 0 mm, that is, when the protrusion 12 is not present in the raw tube region B2, is defined as the standard proof strength Q0. Therefore, in Table 1, when the extended length L of the protrusion 12 is 0 mm, the ratio (= Q _max / Q0) between the maximum proof strength Q _max and the reference proof strength Q 0 is “1”. “Q _max / Q 0” in Table 1 is a dimensionless number indicating an increase rate of the maximum proof stress Q _max with respect to a change in the extension length L of the protrusion 12.

FIG. 5 shows a graph in which “L / √ (D · t)” in Table 1 is set as the horizontal axis and “Q _max / Q0” in Table 1 is set as the vertical axis. As shown in FIG. 5, when “L / √ (Dt)” is 2.44 or more, “Q _max / Q0” is 1.049 or more. That is, when extending設長L protrusion 12 satisfy the condition that the steel pipe local buckling屈半wavelength λ of pile 10 (= 199mm) or more, the rate of increase in ultimate strength _{Q max} of the steel pipe pile 10 against shear force Q is 4.9 % Or more. Thus, it was confirmed that the local buckling resistance of the steel pipe pile 10 with respect to the shearing force Q significantly increases when the extension length L of the protrusion 12 satisfies the condition that the local buckling half wavelength λ of the steel pipe pile 10 is greater than or equal to the condition. .

Next, in the above FEM analysis, the outer diameter D of the steel pipe pile 10 is 1000 mm, the plate thickness t of the steel pipe pile 10 is 6.6 mm, the Poisson's ratio ν of the steel pipe pile 10 is 0.30, and the protrusion height h of the protrusion 12 4 mm, the protrusion width w of the protrusion 12 is set to 10 mm, the extended length L of the protrusion 12 is set to 500 mm, and the protrusion interval S of the protrusion 12 is set to 100 mm. That is, the condition that the extended length L of the protrusion 12 is equal to or greater than the local buckling half wavelength λ (= 199 mm) of the steel pipe pile 10 is satisfied.
Under such conditions, when the protrusion inclination angle θ of the protrusion 12 is changed in the range of 10 ° to 90 °, the protrusion inclination angle θ, the maximum proof stress Q _max of the steel pipe pile 10 against the shear force Q, The results of analyzing the relationship with “Q _max / Q0” are shown in Table 2 below.

FIG. 6 shows a graph in which the protrusion inclination angle θ in Table 2 is set as the horizontal axis, and “Q _max / Q0” in Table 2 is set as the vertical axis. As shown in FIG. 6, when the projection inclination angle θ is 30 ° or more, “Q _max / Q0” is 1.053 to 1.085. That is, when the condition that the protrusion inclination angle θ is 30 ° or more is satisfied, the rate of increase in the maximum proof stress Q _max of the steel pipe pile 10 with respect to the shear force Q is 5.3% to 8.5. Thus, when the extension length L of the protrusion 12 satisfies the condition that the local buckling half-wavelength λ of the steel pipe pile 10 is equal to or greater than that, and the condition that the protrusion inclination angle θ is 30 ° or greater, the steel pipe pile 10 against the shear force Q is satisfied. It was confirmed that the local buckling resistance increased significantly.

Next, in the above FEM analysis, the outer diameter D of the steel pipe pile 10 is 1000 mm, the plate thickness t of the steel pipe pile 10 is 6.6 mm, the Poisson's ratio ν of the steel pipe pile 10 is 0.30, and the protrusion height h of the protrusion 12 4 mm, the protrusion width w of the protrusion 12 is set to 10 mm, the extension length L of the protrusion 12 is set to 3000 mm, and the protrusion interval S of the protrusion 12 is set to 100 mm. That is, the condition that the extended length L of the protrusion 12 is equal to or greater than the local buckling half wavelength λ (= 199 mm) of the steel pipe pile 10 is satisfied. In addition, setting the extended length L of the protrusion 12 to 3000 mm means that the protrusion 12 is formed over the entire length of the steel pipe pile 10.
Under such conditions, when the protrusion inclination angle θ of the protrusion 12 is changed in the range of 5 ° to 90 °, the local inclination resistance θ against the protrusion inclination angle θ and the axial force N (maximum against the axial force N). The results of analyzing the relationship with the yield strength are shown in Table 3 below.

In Table 3, N _max (kN) indicates that when the axial force N acting on the steel pipe pile 10 is gradually increased and the steel pipe pile 10 is forcibly deformed, the local buckling is finally applied to the steel pipe pile 10. The axial force N at the time when the maximum proof stress is generated is shown. That is, this N _max indicates the local buckling resistance of the steel pipe pile 10 with respect to the axial force N (maximum proof stress with respect to the axial force N).
The maximum proof stress N _max (= 7580 kN) when the protrusion inclination angle θ is “none” (when the protrusion 12 does not exist on the steel pipe pile 10) is defined as the standard proof stress N0. Therefore, in Table 3, when the protrusion inclination angle θ is “none”, the ratio (= N _max / N0) between the maximum proof stress N _max and the reference proof strength N0 is “1”. “N _max / N 0” is a dimensionless number indicating an increase rate of the maximum proof stress N _max with respect to the change in the protrusion inclination angle θ of the protrusion 12.

7 shows a graph in which the protrusion inclination angle θ in Table 3 is set as the horizontal axis and “N _max / N0) in Table 3 is set as the vertical axis, as shown in FIG. When it is 30 ° or more, “N _max / N 0” is 1.049 to 1.100. That is, when the condition that the protrusion inclination angle θ is 30 ° or more is satisfied, the increase rate of the maximum proof stress Nmax of the steel pipe pile 10 with respect to the axial force N is 4.9% to 10.0%. Thus, when the extension length L of the protrusion 12 satisfies the condition that the local buckling half-wavelength λ or more of the steel pipe pile 10 is satisfied and the condition that the protrusion inclination angle θ is 30 ° or more is satisfied, the steel pipe pile 10 with respect to the axial force N is satisfied. It was confirmed that the local buckling resistance increased significantly.

As described above, from the analysis results shown in Tables 2 and 3 (FIGS. 6 and 7), the protrusion inclination angle θ of the protrusion 12 is determined as a condition for further improving the local buckling resistance of the steel pipe pile 10. A condition of 30 ° or more and 90 ° or less is derived. However, since the adhesion strength between the steel pipe pile 10 and the concrete 30 cannot be sufficiently obtained when the protrusion inclination angle θ is 90 °, in this embodiment, the condition for further improving the local buckling resistance of the steel pipe pile 10 is obtained. The projection inclination angle θ of the projection 12 is 30 ° or more and less than 90 °.

From the analysis results shown in Tables 2 and 3 (FIGS. 6 and 7), as the most preferable condition, a condition that the protrusion inclination angle θ of the protrusion 12 is 30 ° or more and 60 ° or less is derived. Here, 30 ° which is the lower limit value of the protrusion inclination angle θ has a remarkably high increase rate of the maximum proof stress Q _{max with} respect to the shearing force Q and the maximum proof stress N _max with respect to the axial force N as shown in FIGS. Is the value. Further, the upper limit of the protrusion inclination angle θ of 60 ° is such that even if the protrusion inclination angle θ is increased, the rate of increase in the maximum proof stress Q _max for the shear force Q and the maximum proof stress N _max for the axial force N is large. It is a value that does not change.

Next, in the above FEM analysis, the outer diameter D of the steel pipe pile 10 is 1000 mm, the plate thickness t of the steel pipe pile 10 is 6.6 mm, the Poisson's ratio ν of the steel pipe pile 10 is 0.30, and the protrusion height h of the protrusion 12 Is 4 mm, the protrusion width w of the protrusion 12 is 10 mm, the protrusion inclination angle θ of the protrusion 12 is 45 °, and the extending length L of the protrusion 12 is 500 mm. That is, the condition that the extended length L of the protrusion 12 is equal to or greater than the local buckling half wavelength λ (= 199 mm) of the steel pipe pile 10 is satisfied.
Under the above conditions, when the projection interval S of the projection 12 is changed in the range of 0 mm to 300 mm, the local buckling resistance (maximum proof strength against the shear force Q) against the projection interval S of the projection 12 and the shear force Q The results of analyzing the relationship are shown in Table 4 below. In Table 4 below, when the protrusion interval S of the protrusions 12 is 199 mm or less, the condition that the protrusion interval S of the protrusions 12 is equal to or less than the local buckling half wavelength λ of the steel pipe pile 10 is satisfied.

In Table 4, Q _max (kN) is the same as in Tables 1 and 2, when the steel pipe pile 10 is forcibly deformed by gradually increasing the shearing force Q acting on the upper end of the steel pipe pile 10. The shear force Q at the time when local buckling finally occurs in the steel pipe pile 10 and the maximum proof stress is reached is shown. That is, this Q _max indicates the local buckling resistance of the steel pipe pile 10 with respect to the shearing force Q (maximum proof stress with respect to the shearing force Q).
The maximum yield strength Q _max (= 794 kN) when the projection spacing S is “none” (when no projection 12 is present on the steel pipe pile 10) is defined as the standard strength Q0. Therefore, in Table 4, when the protrusion interval S is “none”, the ratio (= Q _max / Q0) between the maximum proof strength Q _max and the reference proof strength Q0 is “1”. “Q _max / Q 0” in Table 4 is a dimensionless number indicating an increase rate of the maximum proof stress Q _max with respect to a change in the protrusion interval S of the protrusions 12.

FIG. 8 shows a graph in which “S / √ (D · t)” in Table 4 is set as the horizontal axis, and “Q _max / Q0” in Table 4 is set as the vertical axis. As shown in FIG. 8, when “S / √ (Dt)” is 2.44 or less, “Q _max / Q0” is 1.022 or more. That is, when the projection spacing S of the projections 12 satisfies the condition that the local buckling half wavelength λ (= 199 mm) of the steel pipe pile 10 or less, the rate of increase of the maximum proof strength Q _max of the steel pipe pile 10 with respect to the shear force Q is 2.2%. That's it. Thus, the condition that the extended length L of the protrusion 12 satisfies the condition that the local buckling half-wavelength λ of the steel pipe pile 10 is greater than or equal to that and the protrusion interval S of the protrusion 12 is less than the local buckling half-wavelength λ of the steel pipe pile 10 ( That is, it was confirmed that the local buckling resistance of the steel pipe pile 10 with respect to the shearing force Q significantly increases when the condition defined by the above expression (3) is satisfied.

As described above, the condition that the extension length L of the protrusion 12 is equal to or greater than the local buckling half wavelength λ of the steel pipe pile 10 (first condition), and the condition that the protrusion inclination angle θ is 30 ° or more and less than 90 ° (second condition). According to the composite structure 1 according to this embodiment that satisfies the condition (third condition) in which the protrusion spacing S of the protrusions 12 is equal to or less than the local buckling half-wavelength λ of the steel pipe pile 10, it is caused by the plate thickness t of the steel pipe pile 10. Between the stiffening region B1 and the raw tube region B2 while satisfying the condition that the balance between the merit and demerit is optimal (the ratio D / t of the outer diameter D and the plate thickness t is 50 or more and 100 or less). It is possible to improve local buckling resistance at the boundary.

  As can be understood from the above analysis results, at least the above-described effects can be obtained as long as the synthetic structure satisfies the first condition. However, in order to further improve the local buckling resistance of the steel pipe pile 10, it is preferable to employ a composite structure that satisfies at least one of the second condition and the third condition in addition to the first condition.

  By the way, in the said embodiment, although the case where the processus | protrusion 12 was formed in all the stiffening area | region B1 (that is, the processus | protrusion 12 was formed in the whole inner peripheral surface 11 which contacts the concrete 30) was illustrated. As long as at least the first condition is satisfied, the protrusions 12 do not have to be formed in the entire stiffening region B1. For example, as shown in FIG. 9, even if the stiffening region B1 includes a region where the protrusion 12 is not formed (flat region A2) and a region where the protrusion 12 is formed (protrusion region A1). Good. However, in order to increase the adhesion strength between the steel pipe pile 10 and the concrete 30, it is preferable that the protrusions 12 are formed in the entire stiffening region B1.

  Further, in the above embodiment, the case where one boundary between the stiffening region B1 and the raw tube region B2 exists in the projection region A1, but for example, as shown in FIG. A composite structure in which two boundaries between the rigid region B1 and the raw tube region B2 exist may be employed. Also in the composite structure shown in FIG. 10, it is necessary to satisfy at least the first condition. That is, in FIG. 10, the extending length L of the protrusion 12 extending upward in the tube axis direction Y from the upper end of the stiffening region B1, and downward from the lower end of the stiffening region B1 in the tube axis direction Y. Both the extended length L of the extended protrusion 12 need to be set to a length equal to or longer than the local buckling half wavelength λ of the steel pipe pile 10.

Moreover, in the said embodiment, although the H-section steel 20 was illustrated as a joining target member joined to the steel pipe pile 10, what kind of joining target member will be used if it has a shape which can be inserted in the steel pipe pile 10? May be.
Moreover, in the said embodiment, although the case where the processus | protrusion 12 was provided in the inner peripheral surface 11 of the steel pipe pile 10, in addition to this processus | protrusion 12, the radial direction outer side of the steel pipe pile 10 from the outer peripheral surface of the steel pipe pile 10 was illustrated. A protrusion that protrudes in a spiral manner along the pipe axis direction Y of the steel pipe pile 10 may be provided.

As described above, according to the above-described embodiment, by satisfying at least the first condition, the cross-sectional rigidity and the member between the stiffening region B1 and the raw tube region B2 at the boundary between the stiffening region B1 and the raw tube region B2. The difference in yield strength is reduced.

Accordingly, the cross-sectional rigidity and member strength from the stiffening region B1 to the raw pipe region B2 are gradually reduced at the boundary between the stiffening region B1 and the raw pipe region B2, and the cross-sectional rigidity and member strength of the steel pipe (steel pipe pile 10) are gradually reduced. It is possible to prevent a sudden decrease in the. Moreover, according to the said embodiment, generation | occurrence | production of the stress concentration with respect to the steel pipe resulting from loads, such as bending force M, axial force N, and shearing force Q, in the boundary of the stiffening area | region B1 of a steel pipe, and the raw pipe area | region B2. Thus, it is possible to prevent the occurrence of local buckling in the raw tube region B2.

Moreover, according to the said embodiment, since the local buckling resistance of a steel pipe can be improved in the boundary of the stiffening area | region B1 and the raw pipe area | region B2 of a steel pipe, in the joining location etc. of a steel pipe and a member to be joined, etc. It is possible to provide sufficient support for building structures and the like.

Moreover, in the said embodiment, when the protrusion (12) of a steel pipe is seen from the inner side of the radial direction X of a steel pipe, the angle between the circumferential direction W of a steel pipe and a protrusion is set to 30 to 90 degrees. Yes.

Thereby, in the said embodiment, the thin site | part of the steel pipe in which a protrusion does not exist does not continue in the cross section of the pipe circumference direction of a steel pipe. As a result, since local buckling resistance of the steel pipe can be improved, it is possible to prevent the occurrence of local buckling in the raw pipe region B2.

Moreover, according to the said embodiment, since the processus | protrusion is provided spirally along the pipe-axis direction Y of a steel pipe, the adhesive strength of a steel pipe and concrete (30) can be improved. Moreover, in order to improve the adhesion strength between the steel pipe and the concrete, the protrusion provided in the stiffening region B1 can be further extended along the pipe axis direction Y of the steel pipe, thereby improving the local buckling resistance. It becomes possible to manufacture a steel pipe efficiently. Furthermore, according to the above-described embodiment, for example, when a steel strip provided with protrusions is formed in a spiral shape, the manufacturing efficiency of the steel pipe can be significantly improved.

  Conventionally, when the purpose is only to ensure the adhesion strength between the steel pipe and the concrete, the steel strip provided with the protrusions is formed into a spiral shape, etc., so that it is 10 ° with respect to the circumferential direction W of the steel pipe. The steel pipe was provided with a protrusion inclined by about -20 °.

  On the other hand, according to the above embodiment, in order to improve the local buckling resistance of the steel pipe by directly using the manufacturing process of the steel pipe provided with the protrusion in order to ensure the adhesion strength between the steel pipe and the concrete. The protrusion can be efficiently provided on the steel pipe by inclining the protrusion at an angle of 30 ° or more with respect to the circumferential direction W of the steel pipe.

  In particular, according to the above-described embodiment, by setting the protrusion inclination angle θ to 30 ° or more and less than 90 ° (most preferably 30 ° ≦ θ ≦ 60 °), the tube wall is collapsed into a bellows shape on the steel pipe. It is possible to surely prevent the occurrence of local buckling. In addition, it is possible to reliably adhere the concrete to the inner peripheral surface (11) of the steel pipe and to sufficiently secure the adhesion strength between the steel pipe and the concrete.

Further, in the above embodiment, when the steel pipe is viewed in a cross section parallel to the pipe axis direction Y, the convex cross section of the protrusions is arranged along the pipe axis direction Y at intervals equal to or less than the local buckling half wavelength λ of the steel pipe. . That is, the protrusion interval S between the protrusions is set to be equal to or less than the local buckling half wavelength λ of the steel pipe.

This makes it possible to prevent local buckling from occurring in the raw pipe region B2 due to the load acting on the steel pipe between the protrusions adjacent to each other along the pipe axis direction Y of the steel pipe.

Further, by setting the projection spacing S of the projections to be equal to or less than the local buckling half wavelength λ of the steel pipe, the local buckling resistance of the steel pipe is further strengthened, and as a result, the member strength of the steel pipe can be remarkably improved. Become.

As mentioned above, although one Embodiment of this invention was described in detail, this invention is not limited to embodiment mentioned above, The technical scope of this invention must not be limitedly interpreted by the said embodiment.

For example, a projection is provided on a steel pipe used as a pillar material or a sheath pipe, and a pillar material (member to be joined) is inserted into a sheath pipe to which a beam material is joined, and concrete is interposed between the sheath pipe and the pillar material. The present invention can also be applied to a joint structure between a filled column and a beam.

1: Composite structure 12: Projection 10: Steel pipe pile (steel pipe)
20: H-section steel (member to be joined)
11: Inner peripheral surface 30 of steel pipe pile (steel pipe): Concrete 13: Buckling region L: Extension length A1: Projection region A2: Flat region B1: Stiffening region B2: Raw tube region W: Circumferential direction X: Radial direction Y: Pipe axis direction

Claims (2)

With steel pipes;
A joining target member having one end inserted into the steel pipe;
Concrete filled between the inner peripheral surface of the steel pipe and the one end of the member to be joined;
With
The steel pipe has a protrusion that protrudes inward in the radial direction of the steel pipe from the inner peripheral surface of the steel pipe and spirally extends along the pipe axis direction of the steel pipe,
When the region in contact with the concrete on the inner peripheral surface of the steel pipe is defined as a stiffening region and the region not in contact with the concrete on the inner peripheral surface of the steel pipe is defined as a raw tube region, the protrusion is It extends in the spiral shape along the tube axis direction so as to straddle the boundary between the stiffening region and the raw tube region,
The extension length of the projection in the pipe axis direction in the raw pipe region is equal to or greater than the local buckling half wavelength of the steel pipe,
When the projection is viewed from the inside in the radial direction of the steel pipe, an angle between the circumferential direction of the steel pipe and the projection is 30 ° or more and less than 90 °,
When the local buckling half wavelength of the steel pipe is defined as λ (mm), the outer diameter of the steel pipe is defined as D (mm), and the plate thickness of the steel pipe is defined as t (mm), the local buckling half wavelength λ is A composite structure represented by the following formula (1), wherein a ratio D / t between the outer diameter D and the plate thickness t of the steel pipe is 50 or more and 100 or less.

When the steel pipe is viewed in a cross section parallel to the pipe axis direction, the convex cross sections of the protrusions are arranged at intervals of the local buckling half-wavelength λ or less along the pipe axis direction. Item 2. A synthetic structure according to Item 1 .

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